Radio waves are electromagnetic waves that are commonly used to communicate data between antennas. In general, most antennas radiate either linear or circularly polarized radio waves. A linear polarized antenna radiates with its electric field wholly in one plane containing the direction of the radio wave's propagation. Linear polarization is typically classified as either being vertical or horizontal. This classification is determined based upon the electrical field plane of the radio wave radiated by the antenna. An antenna is said to be vertically polarized when its electric field is perpendicular to the Earth's surface and horizontally polarized when its electric field is parallel to the Earth's surface. Additionally, intermediate angles between vertical and horizontal are also possible. A polarization having an intermediate angle is commonly called slant polarization.
In a circularly polarized antenna, the electric field rotates in a circular pattern around the propagation direction making one complete revolution during each wavelength. If the rotation as a function of time is clockwise looking in the direction of propagation, the polarization sense is called right-hand-circular (“RHC”) polarization. If the rotation is counterclockwise, the polarization sense is called left-hand-circular (“LHC”) polarization.
A common method for increasing the data capacity of radio waves within a specified frequency bandwidth involves controlling the radio wave's polarization. Antennas can be designed to transmit and receive a specific polarization, such as a specific linear polarization or a specific circular polarization. Data capacity can be increased by simultaneously using the same frequency spectrum at the orthogonal polarization. Conventional antenna designs allow for a single antenna to transmit and receive two orthogonal polarizations by using two separate ports. However, these designs are more complex and more expensive than single polarization designs. Dual polarization designs can employ a set of radiators with one polarization and an independent set of radiators with the orthogonal polarization. Alternatively, dual polarization designs can employ a single set of radiators, each of which provide two ports for the two orthogonal polarizations. Both methods are significantly more complex than a single port, single polarization design. What is needed in the art is a cost-effective mechanism for switching or controlling the polarization sense of a single polarization antenna. Another need exists in the art for a mechanism that allows for remote controlling or switching of an antenna's polarization sense.